1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to improvement of dimples of golf balls.
2. Description of the Related Art
Golf balls hit by a golf club make a flight with accompanying back spin. The back spin results in lift force that acts on the golf ball. The lift force leads to satisfactory height of a trajectory and flight duration of the golf ball, whereby a great flight distance can be achieved.
Due to excessive backspin, a great drag acts on the golf ball. The drag can reduce the flight distance. In light of suppression of the drag, the spin rate is preferably lower. However, low spin rate may result in insufficient lift force.
Golf balls in recent years achieve both a low spin rate and a great launch angle. A great height of the trajectory and flight duration can be attained by a great launch angle. A great launch angle compensates for insufficiency of the lift force. However, this complementation is not enough.
Japanese Unexamined Patent Application Publication No. 2002-186684 (U.S. Pat. No. 6,780,128) discloses a golf ball having dimples with large size. A great lift force can be attained by the dimples with large size even though the spin rate is low. However, the drag is not sufficiently suppressed according to this golf ball.
Japanese Unexamined Patent Application Publication Nos. Hei 9-70449 (U.S. Pat. No. 5,735,757), 2000-279553 (U.S. Pat. No. 6,368,238) and 2004-321529 (U.S. Pat. No. 6,986,720) disclose golf balls having dimples with a contrived cross-sectional shape. However, these golf balls still exhibit insufficient lift force when the spin rate is low.
Top concern to golf players for golf balls is their flight distance. There exists room for improvement of flight performances of the golf balls. An object of the present invention it to provide a golf ball that is excellent in the flight performance.